JPH0863840A - Vtr head drum in which diamond-like hard carbon film is coated doubly and method and equipment for forming said coating layer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a composition device which is suitable for mass-production by minimizing the friction between a head drum and a tape, improving the wear resistance and lubricity of the drum and protecting the tape, and uniformly forming a coating layer on a cylinder type disk substrate like the head drum without any special operation. SOLUTION: On the 1st coating layer 43 of a high-hardness diamond hard carbon film, the 2nd coating film 44 of a low-hardness diamond type hard carbon film to coat the disk with the double films which have mutually different characteristics. The hardness of the 2nd coating layer is less than that of the 1st coating layer. The double coating is carried out by the composition delay having a sample support base 2 which is mounted with the head drum and sticks on a power source electrode 1 and a reactor having a circular ground electrode 3 which is arranged concentrically at a specific distance from the surface of the laminated head drum. The sample support base includes a ring for space compensation for stably laminating the head drum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a VTR head drum and a method for manufacturing the same, and more particularly, to a VTR head drum made of A1 alloy by double coating diamond hard carbon films having different characteristics. The present invention relates to a VTR head drum capable of improving abrasion resistance and lubricity of a drum and protecting a tape, and a method and apparatus for forming a coating layer thereof.

[0002]

2. Description of the Related Art As video tape recorders (VTRs) have become smaller, lighter and more sophisticated, the air gap thickness between the VTR tape and the head drum has been reduced to minimize friction. The likelihood of contact between the tape and the drum is decreasing and increasing. Such a tendency has recently become severe by introducing a jog shuttle function into a general-purpose VTR, and the wear between the drum and the tape has a great influence on the life. In order to reduce the size of the VTR, the tape must be stably run even with a small driving force, and for this purpose, it is necessary to minimize the friction between the tape and each component of the VTR.

On the other hand, 199 of Nikkei Electronics Asia
According to the standard specifications for digital VTRs and VTRs for HDTVs, which are described on page 40 of the September 3 issue, information storage and reproduction speeds are twice as fast as the present. Since such high-speed information processing is achieved only by improving the rotation speed of the drum, the drum rotation speed of the next-generation VTR is expected to reach 9000 rpm. However, at the above speed, abrasion between the drum and the tape becomes a more serious problem.

Therefore, there is an intention to solve such a problem. For example, Lee Kwang-ryol and Yin Kwang-yong, Bulletin of Korean Institute of Metals, 6 (4), 19
According to a paper published in 1993, diamond-like hard carbon film has excellent mechanical properties, acid resistance and lubricity, so it is used as a protective coating for magnetic recording media (such as hard disks for computers) and for micromachines. It is described as a material that has been applied and researched in many fields, such as lubrication coating, coating of various cutting materials such as razors, protective coating of optical fibers, and coating of ecological materials such as artificial joints. Also, H. Thin Solid F by H. Nakaue
ilms, Vol. 212 (1992), p. 240, published the results of a study to improve the performance and durability of VTR by coating a diamond-like hard carbon film on the side of the drum that contacts the tape. There is.

However, the drum coated with the diamond-like hard carbon film was mounted on a VTR and tested. As a result, the VTR tape was damaged and the magnetic powder and the binder separated from the VTR tape covered the surface of the drum. A serious pollution problem was discovered. Further, the separated magnetic powder has a high hardness, which causes severe damage to the head. This problem is caused by the coating, which greatly improves the surface hardness of the drum, and damages the tape due to the coating defects and the corners of the drum existing on the surface of the drum.

[0006]

Therefore, there is a problem in practical application of the diamond-like hard carbon film coating method proposed for improving durability as an alternative to the friction between the head drum and the tape. There remains a need to find ways to improve the wear resistance and durability of drums without causing damage and drum surface contamination problems.

Accordingly, it is an object of the present invention to provide a VTR head drum which minimizes friction between the head drum and the tape, improves wear resistance and lubricity of the drum, and at the same time protects the tape. To do. That is, to provide a head drum coated with a diamond-like hard carbon film so as to minimize the damage of the tape by the coated drum and prevent the surface contamination of the head drum during actual use based on the head drum coating.

Another object of the present invention is to provide a synthesizing apparatus which can uniformly form a coating layer on a cylinder type circular substrate such as a head drum without any special operation and is suitable for mass production. .

[0009]

In accordance with one aspect of the present invention, the foregoing objects are provided in coating a VTR head drum with a diamond-like hard carbon film to minimize damage to the tape by the coated drum. In addition, a film 44 having a lower hardness is coated on the film coating layer 43 having a higher hardness formed on the head drum, and the diamond-like hard carbon film having different characteristics is double-coated on the head drum. can do.

According to another feature of the present invention, the above-mentioned objects are vacuum system 10-2, gas supply system 10-3, and power supply system 1.
This is achieved by the synthesizer 10 composed of 0-4 and the reactor 10-1. The reactor 10-1 includes a power electrode 1 and
The head drums 24, 25 are brought into contact with the power electrode 1
For supporting the test piece support 2, a circular ground electrode 3 arranged on a concentric circle spaced apart from the surface of the stacked drum by a constant distance, and for insulating the electrode from the outer shell of the reactor 10-1. The insulating part 4 is included. The sample support base 2 is arranged in a vacant space in the sample support base 2 and the power electrode contact portion 21 around which the head drum is stacked, in contact with the power supply electrode 1, and the head drum is flattened. Space compensation rings 26 and 27 for stacking and stably fixing, a top cap 22 of a good conductor arranged above the power electrode contact portion and the head drum stacked, and a top cap of the good conductor. An insulating cap 23 is included.

[0011]

Therefore, the double coating of the diamond-like hard carbon film according to the present invention is applied to the head drum, and the diamond-like hard carbon film produced by the method recently proposed for improving the wear resistance of the head drum. Since the abrasion resistance and lubricity of the head drum can be improved without causing the problem of tape damage due to the coating layer, the requirements for downsizing, weight saving and high performance of the VTR can be satisfied without deterioration of VTR performance. In addition, the life can be improved.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS Other features and advantages of the invention, including the features and advantages of the invention described above, will now be described with reference to the accompanying drawings, in which like reference numerals refer to like elements. , Can be clearly recognized by a person skilled in the art.

First, the principle and configuration of the present invention will be described with reference to FIGS. 2 and 3. As previously mentioned, head drum wear is reduced by coating the surface with a diamond-like hard carbon film to reduce head drum wear. However, since the hardness of the coating layer increases, when there are defects on the coating layer, the friction coefficient greatly increases even for small defects,
The tape is worn by this coating during operation,
As a result, the surface of the drum is contaminated and the performance of the head drum is deteriorated. Therefore, in order to protect the head drum, the hardness of the drum surface is increased, but the hardness of the portion in contact with the tape needs to be low.

Mechanical properties and physicochemical properties such as hardness of the diamond-like carbon film greatly depend on the energy of ions used for synthesis. In the plasma CVD method, it is known that the energy of ions is proportional to the bias voltage of the substrate. Therefore, in order to investigate the hardness characteristics of the diamond-like hard carbon film, the inventors of the present invention used 100% methane and changed the bias voltage from 0V to -600V at a reaction pressure of 1 Torr and a high frequency current of 300mA. To form a diamond-like hard carbon film while changing the DC voltage so that the Knoop micro-hardness value of the diamond-like hard carbon film changes depending on the magnitude of the bias voltage formed on the drum substrate. investigated.

The results are shown in FIG. As can be seen from FIG. 2, the hardness of the diamond-like hard carbon film has a bias voltage of about -90V to -550V.
Hardness increases from 1400 Kgf / mm ² to 2 as V increases
It showed a tendency of monotonically increasing to 050 Kgf / mm ² . Therefore,
Utilizing the characteristics shown in FIG. 2 on the diamond-like hard carbon film coated with the head drum,
The problem described above can be solved by forming a diamond-like low hardness carbon film having a hardness lower than that of the coating layer.

That is, as shown in FIG. 3, first, a transition forming layer 42 for improving the adhesive force of the film is formed on the drum substrate 41 of A1 alloy, and the durability and abrasion resistance of the head drum are formed thereon. A first coating layer 43 for protecting the drum surface is formed to increase wear resistance. By the way, this coating layer 43 forms a diamond-like hard carbon film under the condition that the bias voltage of the substrate is high, so that the film has a high hardness.

Next, a second tape-protecting coating layer 44 is formed on the first coating layer. The second coating layer 44 is formed with a low bias voltage of the substrate to form a low hardness film. The hardness of the second coating layer 44 formed minimizes the abrasion of the tape by the coating layer. Therefore, the hardness should be low.

The above-mentioned double coating operation of the films having different characteristics can be achieved by using the synthesizing apparatus described in detail below. The bias voltage of the substrate can be divided into a self-bias voltage formed by plasma generated by the applied high frequency power source and a DC bias voltage by the DC power source applied independently of the bias voltage. Therefore, in order to appropriately reduce the bias voltage of the substrate, a method of cutting off the DC power supply and using only the self-bias voltage generated by high frequency, and a method of reducing the voltage of the high-frequency power supply and lowering the self-bias voltage Both can be used.

The operation of forming a double coating having different characteristics on the surface of the head drum can be performed by the synthesizing apparatus 10 shown in FIGS. 1 (a) and 1 (b). As shown in FIG. 1 (a), the synthesizer 10 is mainly composed of four parts, a reactor 10-1, a vacuum system 10-2, a gas supply system 10-3 and a power supply system 10-4. . The vacuum system 10-2 and the gas supply system 10-3, the power supply system 10-4, are named “Diamond-like hard carbon film forming method” which was filed by the applicant of the present application on Jan. 7, 1994. It is similar to the plasma CVD apparatus presented in patent application No. 94-201. Therefore, also in this device, as described in Korean Patent Application No. 94-201, the bias voltage of the substrate and the plasma current, which are the main variables of formation, can be independently adjusted. Therefore, the detailed description of the portions similar to the patent application No. 94-201 is omitted in the present specification.

This apparatus, which is one of the preferred embodiments of the diamond-like hard carbon film synthesizing apparatus according to the present invention, uses as a main power source a high frequency of 100 KHz to 15 MHz in which the density of generated plasma and the energy of ions are high. Further, the electrodes are arranged so that uniform formation can be performed on a circular substrate based on the plasma CVD method in which a direct current is combined to adjust the ion energy.

The reactor 10-1 will be described in detail below.
An electrode 1 to which power is supplied is provided at the center of the lower end of the reactor, and V
The sample support base 2 on which the TR head drum is laminated is attached to the electrode 1. From the surface of the drum laminated on the specimen support base 2 1
A circular shield type ground electrode 3 is provided on concentric circles separated by about 10 cm to 10 cm. The distance between the surface of the drum and the ground electrode is 1 cm
If less than, while the plasma is locally generated,
A non-uniform rate of coating is provided on the circumference. As the distance increases, the plasma uniformity increases, but when the distance becomes 10 cm or more, the plasma uniformity does not increase any more. Therefore, if the ground electrode is installed at a distance of 10 cm or more, the size of the synthesizer is too large, which makes the synthesizer uneconomical.

This embodiment will be described in more detail as follows. That is, the optimum high frequency for forming a diamond-like carbon film on the head drums 24 and 25 and the high frequency for determining the distance from the surface of the laminated drums to the ground electrode 3 are 100 KHz and 250.
KHz, 500 KHz and 13.56 MHz were changed and the distance was changed from 1 cm to 10 cm. The pressure was changed from 0.1 Torr to 1 Torr. Further, using methane gas, a high-frequency voltage of 700 V was formed for 10 minutes, and then the change in the surface temperature of the drum was measured. The surface temperature tended to increase as the pressure increased and the frequency decreased. This is because the plasma density and ion energy increase. Since high ion energy and high surface temperature of the drum are advantageous for forming the A1-C mixed layer at the interface between the drum and the diamond-like carbon film, the lower the frequency and the higher the pressure, It can be seen that it is advantageous for formation. However, care must be taken not to overheat the temperature of the drum as it is impossible to cool the drum with cooling water for coating the drum. In this embodiment, the drum temperature is 10
A condition of 250 KHz and 1 Torr was used to keep the temperature below 150 ° C even after a minute.

The distance between the ground electrode and the drum surface has many effects on the plasma uniformity on the circumference. When the distance was shortened under a constant pressure, plasma was locally generated, and this tendency was more intense at lower pressures. The localized generation of plasma on the circumference results in a non-uniform film coating thickness. The uniformity of the plasma increased as the distance increased, and the minimum distance at which the plasma was uniformly generated decreased with increasing pressure. It is necessary to optimize this distance because extending this distance will lead to larger equipment. In this example, it was concluded that it is preferable to set the distance to 4 cm at 1 Torr.

Since the electrode arrangement having such a form generates a very uniform plasma on the surface of the circular sample, the sample is rotated to uniformly coat the surface of the sample such as a head drum. It has the advantage that no other operations need to be performed. Further, by connecting a large number of plasma generators each having a pair of a power electrode and a ground electrode in parallel, it is easy to expand the apparatus to mass production.

Referring to FIG. 1 (b) showing a detailed cross section of the sample support base 2 according to the present invention, the sample support base 2 is A1.
Alternatively, it is connected to the power supply via the power electrode 1 through the power electrode contact portion 21 made of a good conductor material such as stainless steel. Upper head drum 24 and lower head drum 2
Using the central hole of 5, the test piece support base 2 is alternately laminated.
By compensating the space between the upper surface of the upper head drum formed at this time and the lower surface of the lower head drum laminated thereon by using the space compensating ring 26, the surface of the laminated drum is smoothed. Try to be. Also,
A space resulting from the difference in size of the central holes between the upper head drum and the lower head drum, that is, a space between the power electrode contact portion 21 and the head drum having a relatively large central hole in the upper and lower head drums. By compensating with the space compensating ring 27, the position of the head drum is stably fixed. An upper cap 22 of a good conductor for fixing the laminating drum is provided on the upper end of the stack, and a teflon (teflo) is provided on the upper end of the cap.
The insulating cap 23 is formed using an insulating material such as n) to insulate. The insulating cap 23 can be formed of any insulating material.

Although the present invention has been described above centering on the method for forming a multilayer film using the CVD method, the technique for forming a multilayer film according to the present invention is not limited to this. As a method for forming a diamond-like hard carbon film, many methods such as an ion deposition method, an ion plating method, an ECR method, a sputtering method, and a laser ablation method are known. The hardness of the diamond-like hard carbon film can be easily changed by forming conditions in each of the above methods, particularly by converting ion energy.

The head drum double coated with the diamond-like hard carbon film according to the present invention, the head drum coated with a single characteristic diamond-like hard carbon film, the head drum coated with TiN, and the coated head drum The effect and excellence of the double-coated head drum according to the present invention will be described in detail based on the results of experiments performed to compare the characteristics and performance of the uncoated head drum.

Experiment 1: Single diamond-like hard carbon
Film coated head drum and coaty
Unheaded head drum and TiN coated
Comparison of characteristics with a coated head drum A friction coefficient of a head drum coated with a single diamond-like hard carbon film, a head drum coated with TiN and an uncoated head drum was compared and analyzed.

As shown in FIG. 1 (b), 4 sets of VTR head drums having a diameter of 62 mm were laminated on a sample support base and mounted on the diamond-like hard carbon film synthesizing apparatus shown in FIG. The applicant filed a Korean patent application dated January 7, 1994, entitled “Adhesion Strengthening Method for Diamond-like Hard Carbon Film”, and application number 9
Pretreatment such as plasma washing and transition formation were performed by the method presented in No. 4-202. After that, using methane, reaction pressure 1 Torr, high frequency current 300mA, DC current 119m
A diamond-like hard carbon film was formed under conditions of A and substrate bias voltage of -550V for 40 minutes. The diamond-like hard carbon film had a thickness of 1.0 μm and showed a uniform thickness in the circumferential direction. The friction coefficient between the drum and tape before and after the abrasion resistance test was performed on the head drum coated with a single diamond-like hard carbon film thus formed, the head drum coated with TiN and the head drum not coated with TiN. For the measurement, the wear tester presented in the specification of Korean Patent Application No. 94-9687 named "Apparatus Applicant's Abrasion Characteristic Test on Side of Cylinder Object and Measuring Method of Friction Coefficient and Its Apparatus" is used. Measured.

FIG. 4 shows the tension applied to the tape before the abrasion resistance test.
The coefficient of contact friction between the VTR tape according to the (tension) and the coated drum is shown graphically. Referring to FIG. 4, the coefficient of friction of a head drum coated with a single film layer at a rotational speed of 50 rpm, which is a contact friction condition, is 0.2, which is an uncoated drum or a TiN coated drum. The friction coefficient is slightly smaller than 0.25. Further, as shown in FIG. 4, when the diamond-like hard carbon film is coated, the dependence of the friction coefficient on the applied tension is remarkably low.

In FIG. 5, a tension of 400 gf was applied to the drum, an abrasion test was conducted for 4 hours under conditions of 3000 rpm and 0 rpm for 10 seconds each, and the contact friction coefficient measured was shown in a graph. In the case of the uncoated drum or the drum coated with TiN, the friction coefficient increases remarkably compared to before the abrasion resistance test, and due to the change of applied tension, 0.27 to 0.43 and 0.24 to 0 respectively. A value in the range of 0.3 was shown. However, the friction coefficient of the drum coated with the diamond-like hard carbon film showed a value in the range of 0.2 to 0.25 depending on the change in applied tension.

On the other hand, at 1500 rpm, which forms an air gap between the surface of the drum and the tape, all the specimens had a very small coefficient of friction of 0.05 before the abrasion test, but they were coated after the abrasion test. The drum that is not installed has a tension of 0. 0 due to the applied tension increasing from 200 gf to 600 gf.
Friction coefficient values in the range of 16 to 0.42 were exhibited, with TiN coated drums exhibiting friction coefficients in the range of 0.1 to 0.22. However, the drum coated with the diamond-like hard carbon film showed a value almost similar to that before the abrasion test. This means that in the case of a drum coated with a diamond-like hard carbon film, the abrasion resistance test shows almost no surface damage. After the abrasion resistance test, the flat microstructure was severely damaged in the uncoated drum, but no surface damage was observed in the diamond-like hard carbon film coated drum.

Experiment 2: Single diamond-like hard carbon
Mounting test of film-coated head drum The drum in Test Experiment 1 was mounted on a VTR and the temperature was 40 ° C.
Running test with relative humidity 70%, temperature 30 ℃, relative humidity 4
At 0%, FF (11 seconds), REW (9 seconds), CUE (11 seconds),
1000 mode conversion tests under the same conditions as REV (8 seconds)
Repeatedly administered for a time.

As a result of this mounting test, it was observed that many foreign substances adhered to the surface of the drum coated with the single diamond-like hard carbon film. This foreign substance was found to be the magnetic powder and the binder separated from the tape by EDS analysis. As can be seen from this test, when only a film having high hardness is coated, the drum protecting effect is excellent, but there is a problem that the tape is seriously damaged.

Experiment 3: Diamonds having different characteristics
Dora double coated with hard carbon film
Beam characteristics test and implement test First, after forming a first diamond-like hard carbon film 10 minutes under the same conditions as in Experiment 1 by using the synthesis apparatus 10 shown in FIG. 1, blocks the DC power supply, the reaction pressure 1 To
The second coating layer was formed for 10 minutes under the conditions of rr, high frequency current 250A, and substrate bias voltage -250 to form a double film. The hardness of the second coating layer is 1600 Kgf / mm
² and the hardness of the first coating layer is 2050 Kgf / mm ²
It was set to a lower value than.

The degree of change in the friction coefficient and the degree of wear before and after the abrasion resistance test are similar to those of the head drum coated with the single diamond-like hard carbon film in Experiment 1, and no difference was found. It was However, as a result of the same mounting test as in Experiment 2, no contamination of the head drum surface was observed. As a result, by providing the second coating layer having the low hardness on the first coating layer having the high hardness, the damage of the tape can be minimized while maintaining the wear resistance of the head drum. means.

[0037]

Therefore, by coating the double-layered diamond-like hard carbon film according to the present invention on the surface of the head drum, the performance of the head drum is not deteriorated due to the damage of the tape during VTR operation, and the friction coefficient of the head drum is reduced. It can be lowered and the durability can be increased.

Although the present invention has been described with reference to exemplary embodiments, it is not limited to the embodiments described above.
Those having ordinary skill in the technical field related to the present invention should be able to make various changes or combinations of the exemplary embodiments with reference to the detailed description of the present invention. Understandable. Accordingly, the invention includes all such modifications and embodiments and is limited only by the scope of the following claims.

[Brief description of drawings]

FIG. 1 (a) is a schematic sectional view of a synthesizing apparatus used in the present invention. (B) is a detailed cross-sectional view of the sample support base used in the present invention.

FIG. 2 is a diagram showing measured values of chromium hardness of a diamond-like hard carbon film formed under a high-frequency forming current.

FIG. 3 is a cross-sectional view of a double film coated drum.

[Fig. 4] Uncoated drum before wear test, Ti
3 is a graph showing the contact friction coefficient of a drum coated with N 2 and a drum coated with a diamond-like hard carbon film.

Figure 5: Drum uncoated after abrasion test, Ti
3 is a graph showing the contact friction coefficient of a drum coated with N 2 and a drum coated with a diamond-like hard carbon film.

[Explanation of symbols]

1: Power supply electrode 2: Test piece support 3: Ground electrode 4: Insulation part 21: Power supply electrode contact part 22: Upper end cap 23: Insulation cap 24, 25: Head drum 26, 27: Space compensation ring 41: Drum substrate 42: Intermediate layer for adhesion assistance (transfer forming layer) 43: High hardness layer for drum surface protection (primary coating layer) 44: Low hardness layer for tape protection (secondary coating layer)

Claims (13)

[Claims] 1. A head drum, a coating layer for protecting the head drum formed on the surface of the head drum, and a coating layer formed on the coating layer for protecting the head drum,
A VTR head drum double-coated with films having different characteristics, comprising a low hardness tape protection coating layer having a hardness lower than that of the head drum protection coating layer. 2. A head drum, an intermediate layer for increasing the adhesive force of the film formed on the head drum, a first diamond-like hard carbon film formed on the intermediate layer, and the first layer. A diamond-shaped hard carbon film having a different hardness, the second diamond-shaped hard carbon film having a hardness lower than that of the first diamond-shaped hard carbon film formed on the diamond-shaped hard carbon film; VTR head drum double coated with hard carbon film. 3. A method for forming a diamond-like hard carbon film coating layer on a head drum for protecting a tape while maintaining abrasion resistance of a VTR head drum, wherein pretreatment and transition formation are performed, Forming a high hardness first diamond-like hard carbon film on the transition forming layer under a first substrate bias voltage; and, under a second substrate bias voltage lower than the first substrate bias voltage, the first diamond. Forming a second diamond-like hard carbon film having a hardness lower than that of the hard carbon film on the first film, the double coating layer having different characteristics. 4. The step of forming the second film having a low hardness includes the step of cutting off the direct current power of the synthesizing device.
4. The double coating layer having different characteristics according to claim 3, further comprising lowering the bias voltage so that the substrate bias voltage becomes a substrate bias voltage that forms a diamond-like hard carbon film having a low hardness. Forming method. 5. A diamond having a low second substrate bias voltage is formed by cutting off the DC power supply of the synthesizer and incidentally reducing the voltage of the high frequency power supply in the step of forming the second film having a low hardness. The method of claim 3, further comprising lowering the bias voltage so that the substrate-like bias voltage of the hard carbon film is formed. 6. The step of forming the high hardness first diamond-like hard carbon film is performed for 10 minutes under the conditions of a reaction pressure of 1 Torr, a high frequency current of 300 mA, a direct current of 119 mA, and the first substrate bias voltage of −550 V. The method for forming a double coating layer having different characteristics according to claim 3, 7. The second substrate bias voltage is -250V.
The method for forming a double coating layer having different characteristics according to claim 4 or 5, wherein 8. A synthesizer for forming a multilayer film comprising a vacuum system, a gas supply system, a power supply system and a reactor electrically connected to the power supply system, wherein the reactor is A power electrode arranged at the center of the lower end of the reactor, a test piece support base that is in contact with the power electrode and on which the head drum is laminated, and a concentric circle that is separated from the surface of the laminated head drum by the same distance. And a circular ground electrode that is arranged. 9. The synthesizing apparatus of claim 8, wherein the reactor further includes an insulating part for insulating the electrode from the outer shell of the reactor. 10. The test piece support base is disposed in a power electrode contact portion that is in contact with the power supply electrode and an empty space in the test piece support base to fix the head drum flatly and stably. A space compensating ring, an upper cap of a good conductor arranged above the head electrode laminated with the power electrode contact portion, and an insulating cap arranged on the upper cap of the good conductor. Item 8. The synthesizing apparatus according to item 8. 11. The space compensating ring compensates for a space between an upper surface of the upper head drum and a lower surface of the lower head drum laminated on the upper head drum, and a first space for flatly laminating the head drum. Compensation ring and second space compensation for compensating the space between the power electrode contact portion and the head drum having a relatively large central hole in the upper and lower head drums to stably fix the head drum. The synthesizing apparatus according to claim 10, further comprising a ring. 12. The synthesizing apparatus according to claim 8, wherein the circular ground electrode is separated from the surface of the laminated head drum by 1 cm to 10 cm. 13. The synthesizer according to claim 8, wherein the circular ground electrode is a circular shield-shaped ground electrode.